The overall objective of this project is to obtain a better understanding of the basic mechanisms subserving the control of ventilation and regulation of airway smooth muscle tone. The first project constitutes and effort to control each of three sensory receptor systems independently (pulmonary stretch receptors and 02-and CO2-chemoreceptors) so that their interactions in modulating respiratory activity may be investigated. I will determine the relationships of phrenic and para-recurrent laryngeal nerve activities and tracheal caliber to lung stretch at various constant levels of 02- and CO2- chemical drive in anesthetized dogs. The role of carotid bodies and the influence of anesthesia on these relationships will be investigated. In a second project, interactions between exercise and other factors which affect the control of ventilation will be investigated. In awake goats, the ventilatory response to exercise will be assessed during various acute and chronic treatments which alter resting ventilation and blood gases. The role of chemoreceptors in these responses will be determined. Specific attention will be devoted to the mechanism of hypoxia-exercise interactions in ventilatory control using an experimental preparation which allows perfusion of the carotid body chemoreceptors to be isolated from the rest of the body in an awake exercising animal.